Implantable neurostimulation systems have proven therapeutic in a wide variety of diseases and disorders. Pacemakers and Implantable Cardiac Defibrillators (ICDs) have proven highly effective in the treatment of a number of cardiac conditions (e.g., arrhythmias). Spinal Cord Stimulation (SCS) systems have long been accepted as a therapeutic modality for the treatment of chronic pain syndromes, and the application of tissue stimulation has begun to expand to additional applications, such as angina pectoris and incontinence. Further, in recent investigations, Peripheral Nerve Stimulation (PNS) systems have demonstrated efficacy in the treatment of chronic pain syndromes and incontinence, and a number of additional applications are currently under investigation.
More pertinent to the present inventions described herein, Deep Brain Stimulation (DBS) has been applied therapeutically for well over a decade for the treatment of neurological disorders, including Parkinson's Disease, essential tremor, dystonia, and epilepsy, to name but a few. Further details discussing the treatment of diseases using DBS are disclosed in U.S. Pat. Nos. 6,845,267, 6,845,267, and 6,950,707, which are expressly incorporated herein by reference.
Each of these implantable neurostimulation systems typically includes one or more electrode carrying stimulation leads, which are implanted at the desired stimulation site, and a neurostimulator implanted remotely from the stimulation site, but coupled either directly to the neurostimulation lead(s) or indirectly to the neurostimulation lead(s) via a lead extension. The neurostimulation system may further comprise a handheld external control device to remotely instruct the neurostimulator to generate electrical stimulation pulses in accordance with selected stimulation parameters. Typically, the stimulation parameters programmed into the neurostimulator can be adjusted by manipulating controls on the external control device to modify the electrical stimulation provided by the neurostimulator system to the patient.
Thus, in accordance with the stimulation parameters programmed by the external control device, electrical pulses can be delivered from the neurostimulator to the stimulation electrode(s) to stimulate or activate a volume of tissue in accordance with a set of stimulation parameters and provide the desired efficacious therapy to the patient. The best stimulus parameter set will typically be one that delivers stimulation energy to the volume of tissue that must be stimulated (the target tissue region) in order to provide the therapeutic benefit (e.g., treatment of movement disorders), while minimizing the non-target tissue region that is stimulated. A typical stimulation parameter set may include the electrodes that are acting as anodes or cathodes, as well as the amplitude, duration, and rate of the stimulation pulses.
Significantly, non-optimal electrode placement and stimulation parameter selections may result in excessive energy consumption due to stimulation that is set at too high an amplitude, too wide a pulse duration, or too fast a frequency; inadequate or marginalized treatment due to stimulation that is set at too low an amplitude, too narrow a pulse duration, or too slow a frequency; or stimulation of neighboring cell populations that may result in undesirable side-effects.
For example, bilateral DBS of the subthalamic nucleus has been proven to provide effective therapy for improving the major motor signs of advanced Parkinson's disease, and although the bilateral stimulation of the subthalamic nucleus is considered safe, an emerging concern is the potential negative consequences that it may have on cognitive functioning and overall quality of life (see A. M. M. Frankemolle, et al., Reversing Cognitive-Motor Impairments in Parkinson's Disease Patients Using a Computational Modelling Approach to Deep Brain Stimulation Programming, Brain 2010; pp. 1-16). In large part, this phenomenon is due to the small size of the subthalamic nucleus, which may range from the size of a pea to the size of a peanut, with varying shapes from spherical to kidney-shape. Even with the electrodes are located predominately within the sensorimotor territory, the electric field generated by DBS is non-discriminatory applied to all neural elements surrounding the electrodes, thereby resulting in the spread of current to neural elements affecting cognition. As a result, diminished cognitive function during stimulation of the subthalamic nucleus may occur do to non-selective activation of non-motor pathways within or around the subthalamic nucleus.
Thus, it is crucial that proper location and maintenance of the lead position be accomplished in order to continuously achieve efficacious therapy. Lead displacements of less than a millimeter may have a deleterious effect on the patient's therapy. Because the stimulation region needs to be in the correct location to achieve optimal therapy and minimization of side-effects, stimulation leads typically carry many electrodes (e.g., four), so that at least one of the electrodes is near the target and allow programming of the electrodes to place the stimulation field in that region of interest.
The large number of electrodes available, combined with the ability to generate a variety of complex stimulation pulses, presents a huge selection of stimulation parameter sets to the clinician or patient. In the context of DBS, neurostimulation leads with a complex arrangement of electrodes that not only are distributed axially along the leads, but are also distributed circumferentially around the neurostimulation leads as segmented electrodes, can be used.
To facilitate such selection, the clinician generally programs the external control device, and if applicable the neurostimulator, through a computerized programming system. This programming system can be a self-contained hardware/software system, or can be defined predominantly by software running on a standard personal computer (PC). The PC or custom hardware may actively control the characteristics of the electrical stimulation generated by the neurostimulator to allow the optimum stimulation parameters to be determined based on patient feedback and to subsequently program the external control device with the optimum stimulation parameters.
When electrical leads are implanted within the patient, the computerized programming system may be used to instruct the neurostimulator to apply electrical stimulation to test placement of the leads and/or electrodes, thereby assuring that the leads and/or electrodes are implanted in effective locations within the patient. Once the leads are correctly positioned, a fitting procedure, which may be referred to as a navigation session, may be performed using the computerized programming system to program the external control device, and if applicable the neurostimulator, with a set of stimulation parameters that best addresses the neurological disorder(s).
As physicians and clinicians become more comfortable with implanting neurostimulation systems and time in the operating room decreases, post-implant programming sessions are becoming a larger portion of process. Furthermore, because the body tends to adapt to the specific stimulation parameters currently programmed into a neurostimulation system, or the full effects of stimulation are not manifest in a short period of time (i.e., not observed within a programming session), follow-up programming procedures are often needed.
For example, in the context of DBS, the brain is dynamic (e.g., due to disease progression, motor re-learning, or other changes), and a program (i.e., a set of stimulation parameters) that is useful for a period of time may not maintain its effectiveness and/or the expectations of the patient may increase. Further, physicians typically treat the patient with stimulation and medication, and proper amounts of each are required for optimal therapy. Thus, after the DBS system has been implanted and fitted, the patient may have to schedule another visit to the physician in order to adjust the stimulation parameters of the DBS system if the treatment provided by the implanted DBS system is no longer effective or otherwise is not therapeutically or operationally optimum due to, e.g., disease progression, motor re-learning, or other changes.
Regardless of the skill of the physician or clinician, neurostimulation programming sessions can be especially lengthy when programming complicated neurostimulation systems, such as DBS systems, where patients usually cannot feel the effects of stimulation, and the effects of the stimulation may be difficult to observe, are typically subjective, or otherwise may take a long time to become apparent. Clinical estimates suggest that 18-36 hours per patient are necessary to program and assess DBS patients with current techniques (see Hunka K., et al., Nursing Time to Program and Assess Deep Brain Stimulators in Movement Disorder Patients, J. Neursci Nurs. 37: 204-10), which is an extremely large time commitment for both the physician/clinician and the patient.
Significantly contributing to the lengthy process of programming neurostimulation system is the fact the location of the electrodes relative to the target tissue region is not exactly known when the neurostimulation lead or leads are initially implanted within the brain of the patient. In a typical programming session, the boundaries of a targeted region or structure relative to the electrodes can be determined by observing and recording a substantial amount of clinical information observed during the programming session of each patient is recorded. Typically this is accomplished by incrementally increasing the amplitude of electrical stimulation energy on each individual electrode one at a time, for each amplitude increment, observing and manually recording on a relatively large paper spread sheet, clinical information, such as the types of therapeutic effects and side-effects, the threshold values of these therapeutic effects and side-effects, the extent of these therapeutic effects and side-effects. Based on this observed information, the physician or clinician may determine the electrodes having the greatest influence on the surrounding tissue, whether such influence causes a therapeutic effect or a side-effect, the neurostimulation system can be programmed with the best stimulation parameter sets (i.e., those that maximize the volume of target tissue, while minimizing the volume of non-target tissue).
Notably, as the stimulation level of the electrodes that within the targeted region is incrementally increased, first a therapeutic level is reached, and then unwanted side-effects are reached. The boundaries of the target tissue region are determined to be around the therapeutic level, but below the side-effects level. The electrodes located outside of the target tissue region (in theory) have not therapeutic level, only a side-effect level. Once the boundaries the target tissue region are determined, the neurostimulation system can be programmed, such that the resulting electrical stimulation field covers the target tissue region (i.e., the shape and size of the electrical stimulation matches the shape and size of the target tissue region).
While the manual recording of this clinical information has some utility in facilitating programming sessions, the recorded clinical information is not represented to the physician or clinician in a manner that the physician or clinician can readily taken advantage of in the current programming session, and certainly during subsequent programming sessions where the same physician or clinician will not have access to this recorded clinical information.
To facilitate determination of the location of the electrodes relative to the target tissue region or regions, and even the non-target tissue region or regions, a computerized programming system may optionally be capable of storing one or more anatomical regions of interest, which may be registered within the neurostimulation leads when implanted with the patient.
The anatomical region of interest may be a target tissue region, the stimulation of which is known or believed to provide the needed therapy to the patient. For example, if the DBS indication is Parkinson's disease, the target tissue region may be the subthalamic nucleus (STN) or the globus pallidus (GPi). If the DBS indication is Essential Tremor, the target tissue region may be the thalamus. If the DBS indication is depression, the target tissue region may be one or more of the nucleus acumbens, ventral striatum, ventral capsule, anterior capsule, or the Brodmann's area 25. If the DBS indication is epilepsy, the target tissue region may be preferably the anterior nucleus. If the DBS indication is a gait disorder, the target tissue region may be the pedunculopontine nucleus (PPN). If the DBS indication is dementia, Alzheimer's disease or memory disorders, the target tissue region may be anywhere in the Papez circuit.
The anatomical region of interest may be a non-target tissue region, the stimulation of which is known or believed to provide an undesirable side-effect for the patient. For example, stimulation of medial to the STN may cause eye deviations, and stimulation of the substantia nigra may cause symptoms of depression.
Notably, the anatomical region of interest may not be strictly anatomical, but rather may simply represent some arbitrary volume of tissue that, when stimulated, provides therapy or creates a side-effect. The anatomical region of interest may be naturally defined (e.g., an anatomical structure corresponding to the target tissue volume may naturally provide the boundaries that delineate it from the surrounding tissue) or may be defined by a graphical marking). The anatomical region of interest may be obtained from a generally available atlas, and in the case of DBS, a brain atlas, which may be derived from the general population or a previous patient, or may be obtained from a patient specific atlas derived from, e.g., a magnetic resonant imager (MRI), computed tomography (CT), X-ray, fluoroscopy, ventriculography, ultrasound, or any other imaging modality or a merging of any or all of these modalities.
Although the use of a generalized atlas may be quite helpful when optimizing the stimulation parameters that are ultimately programmed into the neurostimulation system, these types of atlases are not patient specific, and thus, cannot account for patient specific physiology. Even if a patient-specific atlas is used, any errors in registration with the neurostimulation leads may prevent optimized programming of the neurostimulation system.
There, thus, remains a need for a user interface that more efficiently allows the programming of neurostimulation systems.